Introduction_Petrophysics_Part2

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Inroduction to Petrophysics Part 2

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Presentation Transcript

Log Applications - 1 : 

1 Hydrocarbon thickness Porosity Saturation Area Hydrocarbon type Permeability Pressure Lithology Any log can supply other information like depth, temperature Log Applications - 1

Log Applications - 2 : 

2 Hydrocarbon thickness Porosity Saturation Area Hydrocarbon type Permeability Pressure Lithology Magnetic Resonance Borehole Imaging Formation Tester Wellbore Seismic Core Sample Taker Log Applications - 2

What subsurface information is important? : 

3 How easy is it to drill to the reservoir? (Cost of drilling, completing…) What subsurface information is important? What is value of hydrocarbon in place? (Potential value) How easily can the hydrocarbon flow out the well? (Cash flow)

Formation evaluation is critical to understanding the reservoir : 

4 Formation evaluation is critical to understanding the reservoir How easy is it to drill to the reservoir? (Cost of drilling, completing…) What is value of hydrocarbon in place? (Potential value) How easily can the hydrocarbon flow out the well? (Cash flow)

Slide 5: 

5 Introduction Well logs or wireline logs are continuous recordings of well depth versus different petrophysical characteristics of the rocks through which the well is drilled. There are many types of well logs, depending upon the characteristics of the rock being measured.Logging ObjectivesThe main purpose of well logging is: - to provide data for evaluating petroleum reservoirs. - to aid in testing, completion and repairing of the well. To calculate the oil reserve in an oil pool we need to know the following.  Thickness of the oil bearing formation.  Porosity of the formation.  Oil saturation.  Lateral extent of the pool. Logs should always be calibrated with core data to improve interpretations. Wireline Logging

What are the physical measurements? : 

6 What are the physical measurements? Spontaneous Potential – (mV) Natural Gamma Ray radiation (cps) Borehole Diameter – (inches or mm) Resistivity (ohm-m) Conductivity (m-mho) Gamma Rays (cps) Neutrons (cps) Acoustic – transit time (micro seconds/ft)

Slide 7: 

7 Types of Well LoggingWell logging is classified into three broad categories:  Open Hole Logging  Cased Hole Logging  Production LoggingOpen Hole LoggingLogging surveys taken before the hole is cased are called open hole logs. The logs included in this group are:  Electrical surveys (induction, laterolog and microlog logs).  Sonic logs.  Caliper Logs.  Dipmeter Logs.  Radioactive surveys (density, neutron and gamma ray logs).

Slide 8: 

8 Electrical LogsElectrical logs (Induction, laterolog, and microlog) measure the electrical properties of the formation alongwith the formation fluids. Sonic LogsSonic logs measure the elastic or (sound) wave properties of the formation. Caliper LogsCaliper logs measure the size or geometry of the hole.Dipmeter LogsDipmeter logs measure dip of the formations.Radioactive LogsGamma ray & neutron logs measure radioactive and neutron absorption properties. Density logs measure electron density of the formation which is related to formation density.

Slide 9: 

9 Cased Hole LoggingLogging surveys taken after the casing is lowered are usually categorized as cased hole logs. The surveys included in this group are:  Gamma Ray  Neutron  Temperature  Pulsed Neutron  Cement Bond Log Some of these surveys like the gamma ray, neutron and temperature logs can be run in both open and cased hole wells.

Slide 10: 

10 Production LoggingWell logging surveys taken to improve production or repair the well are termed as production logs. Surveys included in this category are:  Flowmeter  Pressure  Temperature  Fluid Density

INTRODUCTION - WHAT IS LOGGING? : 

11 INTRODUCTION - WHAT IS LOGGING? In situ meas. (vs. depth) of Rock properties Fluid properties When Openhole (before casing) While drilling (LWD / MWD). After drilling (wireline). Cased hole Interpretation for: Geological properties. Petrophysical properties. Production properties. Casing Open hole

Slide 12: 

12 VALUE AND LIMITATIONS OF WELL LOG DATA Strengths Provides remotely sensed values of reservoir properties and fluids. Among the most abundant reservoir data. Presentation results fairly well standardized. Allows evaluation of lateral (map) and vertical (cross section) changes in reservoir properties and fluids. Limitations Indirect measurements. Vertical resolution. Depth of investigation.

What are the physical measurements? : 

13 What are the physical measurements? Spontaneous Potential – (mV) Natural Gamma Ray radiation (cps) Borehole Diameter – (inches or mm) Resistivity (ohm-m) Conductivity (m-mho) Gamma Rays (cps) Neutrons (cps) Acoustic – transit time (micro seconds/ft)

OPEN HOLE LOGGING MEASUREMENTS : 

14 OPEN HOLE LOGGING MEASUREMENTS Caliper Gamma Ray Spontaneous Potential (SP) Acoustic tc, ts Nuclear b, N LOGGING TOOL

CASED HOLE LOGGING MEASUREMENTS : 

15 CASED HOLE LOGGING MEASUREMENTS Gamma Ray Temperature Flow Velocity Caliper Acoustic Nuclear Electromagnetic Mechanical

Petrophysical Logging Tools - Primary : 

16 Petrophysical Logging Tools - Primary

Environmental Corrections : 

17 Environmental Corrections Things to consider; borehole pressure and temperature mudcake thickness fluid salinity (borehole and formation) hydrocarbons (borehole and formation) depth of mud filtrate invasion Mineralogical Bed thickness

SOME QUESTIONS ADDRESSED BYLOG INTERPRETATION : 

18 SOME QUESTIONS ADDRESSED BYLOG INTERPRETATION Geophysicist / Geologist Are the tops as predicted? Are potential zones porous? Formation intervals? Lithology? Hydrocarbons? What type of hydrocarbons? Commercial quantities? Reservoir Engineer How thick is the pay zone? How homogeneous is the zone? Porosity? Permeability? Production Engineer Which zone(s) to complete? What production rates? Any water production? Is zone hydraulically isolated? Will well need stimulation? What stimulation would be best?

WHAT DOES AN OPEN HOLE LOG COST?IT DEPENDS ON... : 

19 WHAT DOES AN OPEN HOLE LOG COST?IT DEPENDS ON... Well type Vertical/Deviated Deep/Shallow Hot/Normal Measurements Depth charge Survey charge Time / location / special procedures Land/offshore Service charge Equipment availability Rig time Wireline/LWD

TYPICAL OPEN HOLE WIRELINE COSTS : 

20 TYPICAL OPEN HOLE WIRELINE COSTS

LOGGING IS COMPARITIVELY INEXPENSIVE! : 

21 LOGGING IS COMPARITIVELY INEXPENSIVE!

Slide 22: 

22 Fig. 3.1: A Logging Truck

WIRELINELOGGINGEQUIPMENT : 

23 WIRELINELOGGINGEQUIPMENT

Slide 24: 

24 Computerized Logging Units (Contd.)Computer-based units offer the following features: All logs are recorded on 4 mm dats. Computer control of the data allows logs to be recorded either logging up or down with all curves on depth. Calibration are performed under programme control and can be performed more quickly, consistently and accurately. Logs can be played back from the data tapes on many different formats. Basic wellsite, processing/analysis of data is available.

Slide 25: 

25

Slide 26: 

26 DETAILS OF WIRELINE LOGGING RIGUP

LOGGING CABLE : 

27 LOGGING CABLE

Log Presentation : 

28 Log Presentation Heading. Curves related to some physical property of rock/casing surrounding the wellbore.

LOG PRESENTATION - THE HEADING : 

29 LOG PRESENTATION - THE HEADING Well location Depth references Well depth Date of log Casing shoe depth Bit size Mud data Type Properties Resistivities Max. Temperature

Slide 30: 

30 LOG PRESENTATION

LOG PRESENTATION - LINEAR GRID : 

31 LOG PRESENTATION - LINEAR GRID

LOG PRESENTATION - COMMON DEPTH SCALES : 

32 LOG PRESENTATION - COMMON DEPTH SCALES Correlation 1:500 or 1:1000 2 in. (1:600) or 1 in. (1:1200) Heavy lines every 100 ft. or 50m Light lines each 10ft or 5m Routine 1:200 or 1:240 (5 in) Heavy lines every 50 ft. or 5 m Medium lines each 10 ft. or 5 m Light lines each 2 ft or 1 m

CHOOSING A LOGGING TOOL : 

33 CHOOSING A LOGGING TOOL It is necessary to choose the right tool to get the desired measurement. Considerations: Type of well ( wildcat or development ). Open hole or cased hole. Hole conditions ( depth, deviation, hole size, mud type ) Examples: Oil based mud : Induction tool Water based salty mud : Laterolog Tool Formation fluid content (fresh/salt connate water). Economics (cost of the job, rig time involved).

TYPES OF LOGS TO BE RUN : 

34 TYPES OF LOGS TO BE RUN Logging suites generally include one resistivity and one porosity device. The logging string will also have other tools like the gamma ray, SP and caliper tools. However, logging suites usually have two porosity devices to give more information about rock type, hydrocarbon type and porosity. Other considerations – to estimate permeability or to take fluid samples – require other special tools like the formation testers.

Radial Fluid and Resistivity Distribution : 

35 Radial Fluid and Resistivity Distribution Water Based Muds Qualitative Distribution of Resistivity (Rmf > Rw) Resistivity Resistivity Rxo Rt Rxo Rt

Slide 36: 

36 NOMENCLATURE FOR ZONES IN AND AROUND THE BOREHOLE

TOOL CALIBRATIONS : 

37 TOOL CALIBRATIONS A logging tool collects data that are converted to porosity, resistivity, and other values. Each tool is calibrated to an industry standard. This ensures that each tool, irrespective of the type of tool or tool history or service company, reads the same value when logging the same formation (normalization may still be required between log). Check tool calibrations before and after a logging job to ensure good quality log data.

LOG QUALITY CONTROL : 

38 LOG QUALITY CONTROL Check all calibrations before and after job. Record a repeat section of about 200 ft to ensure validity of data and to explain abnormal curve response. Compare log response with offset well logs. Keep hole conditions (hole size, mud type, tool centralization) in mind when interpreting log data. Ensure that logging speeds are as recommended by the service company.

DRILLING DISTURBS FORMATION : 

39 DRILLING DISTURBS FORMATION Drilling and rock crushing: Damage zone. Mud systems and invasion: Oil based mud. Small conductivity mud. Shallow invasion. Thin cake. Water based mud: Moderate to very conductive mud Shallow to deep invasion Thin to thick cake

MUD FILTRATE INVASION : 

40 MUD FILTRATE INVASION

Slide 41: 

41 MUD FILTRATE INVASION

Slide 42: 

42 Borehole Rm : Borehole mud resistivity Rmc : Mudcake resistivity Invaded zone Rmf : Mud filtrate resistivity Rxo : Invaded zone resistivity Sxo : Invaded zone water saturation Uninvaded zone Rw : Interstitial water resistivity Rt : Uninvaded zone resistivity Sw : Uninvaded zone water saturation COMMON TERMINOLOGY